Keel coolers are often used to cool mechanical equipment such as engines in a marine vessel. Keel coolers are typically located on the exterior of the marine vessel to enable cool seawater to directly pass over and contact the cooling tubes. The coolant is typically circulated through the cooling tubes and then passed through the engine which helps to cool the engine components, wherein the cycle is repeated, to enable heat to be transferred from the engine to the coolant, and in turn, to the cooling seawater.
In many keel coolers, two headers or manifolds (hereinafter “headers”) are typically provided, with the cooling tubes connected to and extended between them. In such case, the coolant is allowed to pass from the engine into the first header, through the cooling tubes, and into the second header, before being circulated back to the engine. The first header acts as a transfer point for directing coolant from the engine into the tubes, and the second header acts as a transfer point for circulating coolant from the tubes back to the engine.
In such systems, the cooling tubes are often aligned, side-by-side, in a parallel manner with an outer-most tube on each side, and several intermediate tubes between them. For example, a keel cooler may have a total of eight cooling tubes, with six intermediate tubes, and two outer “side tubes,” extending between the two headers. While the intermediate tubes are typically connected to an angled weir located on the header, the side tubes are typically located on and connected to the side walls of the header. In such case, apertures are provided (on the side walls) through which the coolant can pass directly from the header into the side tubes, and vice versa.
The flow rate of the coolant passing through the cooling tubes can have an effect on the efficiency of the keel cooler, i.e., heat transfer is velocity dependent. Accordingly, maximizing the flow rate of the coolant within the confines of the tube dimensions can increase the efficiency of the cooler. In this respect, in conventional keel coolers of this kind, the side tubes are typically exposed to a greater amount of unhindered fresh seawater, due to their location on the sides, than the intermediate tubes, although the intermediate cooling tubes generally tend to have higher overall flow rates than the side tubes. Accordingly, one way to increase the efficiency of keel coolers without changing the dimensions of the cooling tubes is to enhance the flow rate through the side tubes, i.e., bring them to a level closer to that of the intermediate tubes.
In the past, apertures have been provided on the side walls of headers to allow coolant to pass into and out of the side tubes, and these have been circular in shape. Such apertures, however, have not always achieved the desired flow rate levels for enhanced keel cooler efficiency. What is needed, therefore, is an improved aperture design that increases the flow rate through the side tubes, which can enhance the overall heat transfer efficiency and performance of the keel cooler, without having to change the overall construction and dimensions of the keel cooler.